Recently, even higher output from power FETs (field-effect transistors) that are employed in base stations for mobile communications and in satellite communications has been sought. While one way to realize higher power output from an FET is to raise the operating voltage that is applied to it, owing to the fact that the operating voltage is limited by the gate-to-drain breakdown voltage (BVgd) of the FET, measuring the BVgd is a must. Here, “gate-to-drain breakdown voltage” is for example a voltage value defined as, “voltage at which a current of 1 mA per 1 mm gate width flows between gate-drain when a reverse voltage is applied across the two terminals.” Then to date, an appropriate film has been built on a wafer as a substrate; the working device including a Schottky contact (gate) and ohmic contacts (source, drain) has been fabricated; and voltage has been applied across the Schottky contact-ohmic contact.
Nonetheless, with methods of measuring the breakdown voltage of the conventional epitaxial semiconductor wafer just described, issues such as the following have persisted. In particular, if after fabricating a working device onto a wafer the wafer is determined not to be up to standard for carrying out the breakdown-voltage measurement, a great deal of time and expense ends up being lost. Moreover, even cases in which the breakdown-voltage measurement is carried out using a readily-fabricated “large device” (a device, larger than a working device, from which measurements are taken), there has been a problem in that with at least two patterning cycles being necessary—patterning for the Schottky contact serving as the gate, and patterning for the ohmic contacts serving as the source/drain—the fabricating process ends up costing a great deal of time and trouble.